1. Field
The disclosure relates to a hydraulic servo of a clutch for performing and discontinuing power transfer which is for use in, for example, vehicular automatic transmissions and the like. More particularly, the disclosure relates to a clutch-purpose hydraulic servo in which a drum member is disposed as a separate member on a shaft member.
2. Description of the Related Art
Generally, in a hydraulic servo of a clutch for use in, for example, a vehicular automatic transmission or the like, an operating oil chamber is formed between a piston and a cylinder portion, and is equipped with a cancel plate and a return spring for pushing the piston back toward the cylinder portion when the clutch is released. It is necessary that the relative position of the cancel plate be fixed with respect to the cylinder portion. Therefore, for example, the cancel plate is restricted with respect to a clutch drum having the cylinder portion by a snap ring or the like so that the cancel plate does not move to a side opposite from the return spring.
When a clutch is disposed in an automatic transmission or the like, there often exists another member that undergoes substantially the same rotation, such as an input shaft, or a clutch drum of another clutch, etc. If, in such a case, a hub-shaped (sleeve-shaped) member is provided so as to extend at an inner peripheral side of the cylinder portion and a cancel plate is provided on an outer peripheral side of the hub-shaped member, the double structure formed by the hub-shaped member and the member that undergoes the same rotation becomes an impediment to a compact design. This is avoided by the arrangement as described in, for example, Japanese Patent Application Laid-Open No. 2003-247612 (specifically, the members represented by reference numerals 12, 32 in FIG. 3 of the laid-open application). That is, the cancel plate and a member (e.g., a clutch drum) having the cylinder portion are disposed immediately on the outer peripheral side of a member (e.g., an input shaft) that undergoes the same rotation as mentioned above, and the member having the cylinder portion is fixed to the member that undergoes the same rotation by, for example, welding or the like. Therefore, the member having the cylinder portion and the member that undergoes the same rotation are structured integrally as a unit.
However, the integration of the member having a cylinder portion with the member that undergoes the same rotation through fixation thereof by, for example, welding or the like, requires a welding process (integrally forming process) or the like in the assembly of a clutch (automatic transmission), and therefore has the problem of impeding improvement in the ease of assembly and reduction of the production process and the production cost.